Electrostriction at optical frequencies

Electrostriction, the deformation of a dielectric under the influence of an electric field, is of continuous interest in optics. One interesting point is that the classic experiment by Hakim and Higham [Proc. Phys. Soc. 80, 190 (1962)] for a stationary field supports a different formula of the electrostrictive force density than the recent experiment by Astrath et al. [Light Sci. Appl. 11, 103 (2022)] for optical frequencies. In this work, we aim at understanding the origin of this difference by developing a time-dependent covariant theory of electrostriction. We also simulate the propagation of a Gaussian light pulse through a dielectric material. Simultaneously with solving the electric and magnetic fields of the Gaussian light pulse, we solve Newton's equation of motion to find out how the velocity and position distributions of atoms under the influence of the optical force develop as a function of time. We also study the assumptions behind the conventional derivation of electrostrictive forces. This derivation, see e.g., Electrodynamics of Continuous Media by Landau and Lifshitz (1984), is based on field-induced changes in the volume of a dielectric, and it assumes that there is a local thermodynamical balance between the dielectric and the external forces caused by the field. At optical frequencies, this assumption is no longer valid. We expect that the understanding of the role of electrostriction at optical frequencies is useful for improved understanding of thermal coupling of light and dielectrics.